Optical Fiber Hydrogen Sensor

A hydrogen sensor based on evanescent field technology requires an interdisciplinary study. It comprises the study of the thin film for the hydrogen sensing, a surface plasmon resonance, the field distribution around the optical fiber, analysis of the sensor based on the power of evanescent field, the deposition technique of thin film, and the measurement approach and the data processing, etc. To put this technique into industry, it attracts more attention on the following questions: how to integrate different technologies relative together, how to cut the cost of the sensor system and how to improve the performance of the sensor.This thesis introduces the design and implementation of a hydrogen sensors by evanescent field fiber. It mainly studies the hydrogen sensing principle of surface plasmon resonance, the deposition technique of thin film with Pd or Pd99-Ag1 on fibre eroded , the testing technique of the hydrogen sensor. Making use of these technologies mentioned above, our group have developed a kind of hydrogen sensing system.This thesis presents a structure of a hydrogen sensors by evanescent field fiber. The simulation results show that the sensitivity of the sensor is influenced significantly by the thickness of the film. A highly sensitive system can be achieved when the thickness of the Pd film is in the range from 10nm to 30nm and the hydrogen concentration is in 0~4%. The resolution of the hydrogen sensors we made can reach 0.5% with 60s for responding.This thesis designes a special clamp for etching optical fiber and depositing film on the fiber, an encapsulation set of the characteristics which is dampproof, shake and eroding resisted. The experimental set-up for hydrogen sensing includes the light source, gas cell, mass flow controller, stainless steel helical tubing and the detector, etc. The experimental results are also discussed and the data which are got from the experiment are processed and analysed .This thesis sets up some mathematics models matching some experimental phenomena, and then explains it. It provides a method to improve the manufacture technics.